Properties of PHAs and their Correlation to Fermentation Conditions

Abstract

This paper presents part of the results obtained during an ICBT short term scientific exchange mission at the University of Pisa, Dipartimento di Chimica e Chimica Industriale. Several samples of 3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) with comonomer contents in the range of 2,5 to 76 % were produced in fed batch fermentations with different strains under varying cultivation conditions. These samples were characterized by DSC, TGA, GPC, 1H-NMR. Under certain PHA producing conditions, PHA quality and processability are rather bad due to an inhomogeneous distribution of the 3HV units in the polymer while polymers from other fermentations have excellent properties. Analysis of these fermentation conditions resulted in very important hints for improvement of existing and development of future fermentation processes. A strong dependence of the molecular weight distribution of the polymer on the main carbon source used in the fermentation was also found.